The construction industry requires the massive exploitation of natural resources such as limestone, sand, gravel, gypsum and lumber. The materials are found, almost without exception, in every single edifice or man made structure in the United States. By example, a lightweight construction material, known generically as autoclaved aerated concrete, also known by the acronym AAC, uses the same basic ingredients as in concrete, but in addition, also comprise aluminum powder. The AAC building material requires the mining of silica (SiO2) as the main raw material. The silica is in a coarse state and requires being ground and sieved for utilization as in the production process of the AAC. The preparation of the silica sand for utilization obviously requires expending a substantial amount of energy which further depletes natural resources and adds to the cost of the building material. The construction industry further depletes the forests by requiring huge amounts of lumber in the construction of buildings and residential housing. The AAC is known to replace the need for lumber as a basic structural element. Other material, such as lime, must be added to produce the AAC product.
While the building material industry depletes natural resources such as limestone, sand and gravel, the mining industry is creating waste materials in the form of mine tailings. In particular, in the State of Arizona, there are mountains of waste material containing billions of tons of copper mine tailings. The Arizona copper mines that produce the waste material are porphyry copper mines, where traditionally the host copper containing rock is predominantly silica (SiO2). The average composition of the porphyry copper mine tailings in Arizona, in weight percentage, has been found to consist of:
Silica Sand (SiO2): 61% PA1 Lime (CaO): 12% PA1 Aluminum Oxide (Al203): 7% PA1 Ferrous Oxide (Fe203): 7% PA1 Pyrite (FeS2): 3% PA1 Magnesium Oxide (MgO): 1% PA1 Potassium Oxide (K20): 2% PA1 Sodium Oxide (Na20): trace PA1 Sulfur (S) trace
The composition analysis of the Arizona copper mine tailings shows that silica sand is in fact found in substantial amounts. Also, and a very important characteristic, the silica is found in a granular state that is substantially equivalent to the granular state to which the silica must be ground and sieved to produce the AAC lightweight building material. The fine granular state of the silica sand in the mine tailings results from a flotation process that produces copper from pulverized copper ore. Similarly, lime is found in substantial amounts in the copper mine tailings. While, no particular data is presently available, mine tailings from other metal ore mines conceivably also contain comparable amounts of silica sand and lime in their mine tailings, especially if the host rock for the other metals is porphyritic.
Although the composition analysis of the copper mine tailings shows that silica sand, and lime is readily available, there are no known processes for producing building structural material that have capitalized on the availability of the silica and other of the contained elements in the waste material resource. The mine tailings from metal ore mines, especially the Arizona copper mine tailing, are not being utilized for any useful purpose and are contributing to a form of pollution of the environment. Present day environmental concerns will eventually require cleanup of the copper mine tailings, and other metal ore mining tailings. The utilization of the copper mine tailings, for example, when used to produce the AAC building material, would not only rid the blight of the mountains of mine tailings, but would also preserve the natural resources by using the available silica, lime and other contained elements, and conserve energy by virtue that the silica in the mine tailings does not require the expending of energy to arrive at the desired material gradation for use as a processed silica sand substitute. Further, since the AAC is a substitute for lumber, the forests as a natural resource, would also be preserved.
Thus, a need is seen to exist for a building product produced by a process that minimizes the need for natural resources, conserves on energy, and that uses the mine tailings from mining to effect environmental cleanup.
A particular need is seen to exist for a building material produced by a process that minimizes the need for natural resources used in the building material, that conserves on energy, and that uses copper mine tailings in the production of the building material to effect environmental cleanup.
A more particular need is seen to exist for a building material produced by a process that minimizes the need for processed silica sand and other raw materials by using the available silica sand and other raw materials found in copper mine tailings to effect environmental cleanup.